A rear-view mirror seems to be the only aid to the driver during backing of a car. However, observation through the mirror can hardly reflect the true condition at the rear and the angle of backing cannot be exactly sure. In many occasions, the driver has to turn around to see what is actually happening. This is not only tiresome but also dangerous, especially during foggy weather or a rainy day when visibility is poor.
The present invention is devised to overcome the abovesaid drawbacks.